The San Tomas Aquino Creek watershed covers an area of approximately 45 square miles. San Tomas Creek originates in the forested foothills of the Santa Cruz Mountains flowing in a northern direction through the cities of Campbell and Santa Clara, into the Guadalupe Slough, and finally into the Lower South San Francisco Bay. The major tributaries to San Tomas Aquino Creek include Saratoga, Wildcat, Smith and Vasona Creeks. Of these, Saratoga Creek drains the largest area 17 square miles) and joins San Tomas Creek 1.5 miles upstream of Highway 101. Due to its relatively large size, the Saratoga Creek subwatershed is often viewed as a distinct watershed even though it does not directly drain to the Lower South San Francisco Bay.
Most of the San Tomas Aquino watershed is developed as high-density residential neighborhoods, with additional areas developed for commercial and industrial uses The majority of the San Tomas Aquino Creek channel has been modified and lined with concrete (from the Smith Creek confluence in the upper reaches downstream to Highway 101).
Hitch is the only native fish found in San Tomas Aquino Creek.
Saratoga Creek Subwatershed:
Saratoga Creek originates on the northeastern slopes of the Santa Cruz Mountains along Castle Rock Ridge at 3,100 feet in elevation. Saratoga creek flows for approximately 4.5 miles in an eastern direction through forested terrain, largely contained within Sanborn County Park. It continues for about 1.5 miles through the low-density residential foothill region of the Town of Saratoga and then for another 8 miles along the alluvial plain of the Santa Clara Valley, through the cities of San Jose and Santa Clara characterized by high-density residential neighborhoods.
Major tributaries include San Andres, Bonjetti, and Booker Creeks.
Saratoga Creek supports both warm and cold water native fish assemblages. Three native fish species that have been found in the creek include California roach, Sacramento sucker and rainbow trout.
- Watershed area: 44.8 square miles
- Number of tributary creeks: 15
- Miles of natural creek bed: 50.5
- Miles of Engineered Channel: 15.5
- Local towns and cities: Santa Clara County, Saratoga, Monte Sereno, Los Gatos, San Jose, Campbell, Santa Clara
- Percent area by land use:
- Residential 53.9%
- Industrial/Commercial 18.8%
- Forest 23.7%
- Rangeland 0.8%
- Other 2.8%
- Percent Impervious Area: 60.1%
- Miles of Underground Culvert or Stormdrain: 79.3
- Beneficial Uses: Cold Freshwater Habitat (COLD), Warm Freshwater Habitat (WARM), Wildlife Habitat (WILD), Water Contact Recreation (REC-1), Noncontact Water Recreation (REC-2)
- Water Quality Impairments:
- Los Gatos Creek: Urban Pesticide Toxicity (Diazinon)
- Saratoga Creek: Urban Pesticide Toxicity (Diazinon), Trash